Furin-mediated release of soluble hemojuvelin: a new link between hypoxia and iron homeostasis

The liver peptide hepcidin regulates iron absorption and recycling. Hemojuvelin (HJV) has a key role in hepcidin regulation, and its inactivation causes severe iron overload both in humans and in mice. Membrane HJV (m-HJV) acts as a coreceptor for bone morphogenetic proteins (BMPs), whereas soluble HJV (s-HJV) may down-regulate hepcidin in a competitive way interfering with BMP signaling. s-HJV is decreased by iron in vitro and increased by iron deficiency in vivo. However, the mechanisms regulating the 2 HJV isoforms remain unclear. Here we show that s-HJV originates from a furin cleavage at position 332–335. s-HJV is reduced in the cleavage mutant R335Q as well as in cells treated with a furin inhibitor, and increased in cells overexpressing exogenous furin, but not in cells overexpressing an inactive furin variant. Furin is up-regulated by iron deficiency and hypoxia in association with the stabilization of HIF-1α. Increased s-HJV in response to HIF-1α occurs during differentiation of murine muscle cells expressing endogenous Hjv. Our data are relevant to the mechanisms that relate iron metabolism to the hypoxic response. The release of s-HJV might be a tissue-specific mechanism, signaling the local iron requests of hypoxic skeletal muscles independently of the oxygen status of the liver

Hemojuvelin N-terminal mutants reach the plasma membrane but do not activate the hepcidin response

Background Hemojuvelin is a glycosylphosphatidylinositol-anchored protein, expressed in liver, skeletal muscle and heart. As a co-receptor of bone morphogenetic protein, membrane hemojuvelin positively modulates the iron regulator hepcidin. Mutations of the gene encoding for hemojuvelin cause juvenile hemochromatosis, characterized by hepcidin deficiency and severe iron overload. We have previously shown that several hemojuvelin variants do not efficiently reach the plasma membrane, whereas a few N-terminal mutants localize to the plasma membrane. Design and Methods We studied hemojuvelin mutants of N-terminus (C80R, S85P, G99V, ΔRGD) and GDPH-consensus site for autoproteolysis (A168D, F170S, D172E) transiently expressed in HeLa cells, using electron microscopy, morphometric analysis and binding assays at different time points. Hepcidin activation by wild-type and mutant forms of hemojuvelin was assessed in Hep3B cells transfected with a hepcidin-promoter luciferase-reporter construct. Results S85P, G99V and ΔRGD were localized to plasma membrane 36 hours after transfection, but less efficiently exported than the wild-type protein at earlier (24–30 hours) times. Morphometric analysis clearly documented delayed export and endoplasmic reticulum retention of G99V. C80R was exported without delay. GDPH variants were partially retained in the endoplasmic reticulum and Golgi apparatus, but showed impaired plasma membrane localization. In the hepcidin promoter assay only wild type hemojuvelin was able to activate hepcidin. Conclusions The delayed export and retention in the endoplasmic reticulum of some N-terminal mutants could contribute to the pathogenesis of juvenile hemochromatosis, reducing a prompt response of bone morphogenetic protein. However, independently of their plasma membrane export, all hemojuvelin mutants tested showed no or minimal hepcidin activation

mTOR-related synaptic pathology causes autism spectrum disorder-associated functional hyperconnectivity.

Postmortem studies have revealed increased density of excitatory synapses in the brains of individuals with autism spectrum disorder (ASD), with a putative link to aberrant mTOR-dependent synaptic pruning. ASD is also characterized by atypical macroscale functional connectivity as measured with resting-state fMRI (rsfMRI). These observations raise the question of whether excess of synapses causes aberrant functional connectivity in ASD. Using rsfMRI, electrophysiology and in silico modelling in Tsc2 haploinsufficient mice, we show that mTOR-dependent increased spine density is associated with ASD -like stereotypies and cortico-striatal hyperconnectivity. These deficits are completely rescued by pharmacological inhibition of mTOR. Notably, we further demonstrate that children with idiopathic ASD exhibit analogous cortical-striatal hyperconnectivity, and document that this connectivity fingerprint is enriched for ASD-dysregulated genes interacting with mTOR or Tsc2. Finally, we show that the identified transcriptomic signature is predominantly expressed in a subset of children with autism, thereby defining a segregable autism subtype. Our findings causally link mTOR-related synaptic pathology to large-scale network aberrations, revealing a unifying multi-scale framework that mechanistically reconciles developmental synaptopathy and functional hyperconnectivity in autism

Diagnosis of Imported Dengue and Zika Virus Infections in Italy from November 2015 to November 2022: Laboratory Surveillance Data from a National Reference Laboratory

Dengue (DENV) and Zika (ZIKV) viruses are mosquito-borne human pathogens. In Italy, the presence of the competent vector Aedes albopictus increases the risk of autochthonous transmission, and a national plan for arboviruses prevention, surveillance, and response (PNA 2020–2025) is in place. The results of laboratory diagnosis of both viruses by the National Reference Laboratory for arboviruses (NRLA) from November 2015 to November 2022 are presented. Samples from 655 suspected cases were tested by both molecular and serological assays. Virus and antibody kinetics, cross-reactivity, and diagnostic performance of IgM ELISA systems were analysed. Of 524 cases tested for DENV, 146 were classified as confirmed, 7 as probable, while 371 were excluded. Of 619 cases tested for ZIKV, 44 were classified as confirmed, while 492 were excluded. All cases were imported. Overall, 75.3% (110/146) of DENV and 50% (22/44) of ZIKV cases were confirmed through direct virus detection methods. High percentages of cross reactivity were observed between the two viruses. The median lag time from symptoms onset to sample collection was 7 days for both DENV molecular (range 0–20) and NS1 ELISA (range 0–48) tests, with high percentages of positivity also after 7 days (39% and 67%, respectively). For ZIKV, the median lag time was 5 days (range 0–22), with 16% positivity after 7 days. Diagnostic performance was assessed with negative predictive values ranging from 92% to 95% for the anti-DENV systems, and of 97% for the ZIKV one. Lower positive predictive values were seen in the tested population (DENV: 55% to 91%, ZIKV: 50%). DENV and ZIKV diagnosis by molecular test is the gold standard, but sample collection time is a limitation. Serological tests, including Plaque Reduction Neutralization Test, are thus necessary. Co-circulation and cross-reactivity between the two viruses increase diagnostic difficulty. Continuous evaluation of diagnostic strategies is essential to improve laboratory testing

Gaia Early Data Release 3: Structure and properties of the Magellanic Clouds

We compare the Gaia DR2 and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insights into features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones

A first update on mapping the human genetic architecture of COVID-19

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